This is what the Seventh Circuit U.S. Court of Appeals recently held in a case where the plaintiff tried to admit his treating physician as an expert to testify regarding the specific cause of his injuries. The doctor, although a specialist in pulmonology, a subspecialty of internal medicine concerned with diseases of the lungs and bronchial tubes, was not qualified. The plaintiff failed to show that his physician employed a reliable methodology in concluding the injuries were caused by the defendant’s actions.

An amusement park visitor brought a negligence action against the amusement park’s owners. During the Plaintiff’s visit, the filter pump that was connected to the water feature malfunctioned. As the park staff worked to fix the problem, pool chemicals—bleach and hydrochloric acid—accumulated in the pump. When the pump was restarted, the chemicals discharged into the water and a cloud of chlorine gas released into the air. The Plaintiff said he developed chronic asthma and reactive airways dysfunction syndrome (RADS) from inhaling the gas. After the Plaintiff’s causation expert was disqualified, the park owners moved for summary judgment. But the Plaintiff argued that he did not need a causation expert, or alternatively, that his treating physician could serve as an expert.

The Plaintiff saw a pulmonologist after the incident, but waited more than a year before consulting his primary care physician. He then saw a second pulmonologist who diagnosed him with RADS and chronic asthma—more than 14 months after the incident. The pulmonologist based her diagnosis on her evaluation of the Plaintiff, coupled with the results of a pulmonary function study conducted by the pulmonologist that the Plaintiff visited a year earlier.

At trial, the district court found that the causation issue was too complex for an unassisted jury, and held that the Plaintiff’s treating physician’s qualifications and methodology were too uncertain to permit her to opine on the issue. The court granted the park owner’s motion and the Plaintiff appealed.

Circuit Judge Joel Martin Flaum wrote in his opinion that a review of the district court’s decision concerning the admission of expert testimony in the summary judgment context is “slightly more nuanced.” The appellate court will review de novo whether the district court properly followed the Daubert framework, and if so—and in this case, the Plaintiff conceded that, in evaluating the sufficiency of the pulmonologist’s opinion testimony, it did—whether the trial court’s decision to exclude expert testimony was an abuse of discretion.

Under Indiana law, proving negligence requires proof of both general and specific (or individual) causation, and the law of the Seventh Circuit was the same. General causation refers to “whether the substance at issue had the capacity to cause the harm alleged, while ‘individual causation’ refers to whether a particular individual suffers from a particular ailment as a result of exposure to a substance.” The district court found that, without an appropriate expert, the Plaintiff could not establish specific causation—that the inhalation of chemical fumes caused his health conditions. The Plaintiff, however, maintained that he did not need an expert to establish that the incident caused his ailments.

The Plaintiffs argued that, even if a jury would be unable to attribute the onset of these conditions to the events at the park, a jury was capable of concluding that he suffered some injury by inhaling the fumes. He conceded that the causation question would be outside “the purview of laypeople” when dealing with “some chemicals,” but not chlorine—a “gas [that] is a well-known cause of pulmonary injury.” The Seventh Circuit opinion stated that, even if it were to accept such a dubious contention as true, the fact remained that the quantity of chlorine actually inhaled by the Plaintiff was unknown. Given so much uncertainty, Judge Flaum held there was no question that a layperson was incapable of scientifically determining specific causation in this case without the assistance of an expert.

Indiana law says that “questions of medical causation of a particular injury are questions of science necessarily dependent on the testimony of physicians and surgeons learned in such matters.” And that is particularly true in this case, Judge Flaum wrote. Without an expert, a plaintiff in such a complex case would be free to prove his allegations relying on the logical fallacy post hoc ergo propter hoc (“the fallacy of saying that because effect A happened at some point after alleged cause B, the alleged cause was the actual cause”). As a result, the Seventh Circuit held that a causation expert was required.

Judge Flaum next examined if the Plaintiff’s pulmonologist could serve as a causation expert. When the Plaintiff’s originally proposed expert was deemed unqualified to testify, he did not disclose the pulmonologist as an expert witness. Disclosure must be made at least 90 days before the date set for trial. When the Defendant filed its summary judgment motion, the date for filing expert disclosures had passed. The court held that this alone was sufficient justification for granting summary judgment for the Defendant.

Nevertheless, even if the Plaintiff had complied with the Rule 26 expert disclosure obligations, he failed to demonstrate the pulmonologist’s fitness as an expert. Rule 702 and Daubert require the district court to determine whether proposed expert testimony is both relevant and reliable. In so doing, the Seventh Circuit held in 2000 that “[a] district court enjoys broad latitude both in deciding how to determine reliability and in making the ultimate reliability determination.” Here the district court deemed the pulmonologist’s qualifications and her methodology to be too questionable to permit her to testify as an expert witness at the trial.

The Plaintiff argued that the pulmonologist was qualified as a causation expert by “sheer virtue of her status” as a pulmonologist, but that is not enough, the judge held. Treating physicians are no different than any other expert for purposes of Rule 702, Flaum wrote. Prior to proffering expert testimony, “they must withstand Daubert scrutiny like everyone else.” Plaintiff added that because the pulmonologist had 20 years of experience as a board certified pulmonologist, “[i]t goes without saying she understands … reactive airways dysfunction syndrome.” Again, not so, said the judge, who believed that Plaintiff misunderstood the requirements of Daubert and Rule 702.

Although a doctor may have “experience diagnosing and treating asthma … that does not make him qualified to ‘assess its genesis,’” the judge reasoned. Here Plaintiff offered no evidence that the pulmonologist had ever treated another patient for chlorine gas exposure or had any training in toxicology. Nor did the Plaintiff establish that the pulmonologist employed a reliable methodology in forming her causation opinion (assuming she was qualified to do so). The pulmonologist diagnosed the Plaintiff after listening to his own description of his symptoms and the events at the park—14 months after the fact—and after looking at the results (but not the underlying data) of the pulmonary function study conducted by another doctor the year before.

There was no evidence that the pulmonologist considered other possible causes of the Plaintiff’s ailments and, if so, how and why she ruled them out. However, the Plaintiff told the district court that the pulmonologist had assessed the cause of his ailments by employing “differential diagnosis,” which refers to a method of diagnosing an ailment, not determining its cause. “Differential etiology” is a causation-determining methodology. To be validly conducted, an expert must systematically “rule in” and “rule out” potential causes in arriving at his or her ultimate conclusion. The Plaintiff did not show that this was done.

“Many times we have emphasized that experts’ work is admissible only to the extent it is reasoned, uses the methods of the discipline, and is founded on data,” Judge Flaum wrote, citing an earlier Seventh Circuit case. Here, the Plaintiff failed to demonstrate this with respect to the pulmonologist’s causation opinion. It was within the district court’s discretion to deem the pulmonologist unqualified to proffer expert testimony, even without the Plaintiff’s non-compliance with Rule 26.

As a result, the Seventh Circuit affirmed the district court’s grant of summary judgment.

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